A spring probe pin, commonly referred to as a pogo pin, is widely used for an inspection device for a semiconductor wafer, an LCD module and a semiconductor package, and for any kind of socket, a battery connector of a mobile phone, and the like.
FIG. 1 is a cross-sectional view of a related pogo pin.
Referring to FIG. 1, a pogo pin 10 includes an upper probe 12, a lower probe 14, a spring 16 for applying elastic force to the upper and lower probes 12, 14, and a cylindrical body 18 for receiving a lower end of the upper probe 12, an upper end of the lower probe 14 and the spring 16.
Each of the upper and lower probes 12, 14 is engaged at one end thereof by the cylindrical body 18 so that the upper and lower probes 12, 14 may be prevented from being escaped from the cylindrical body 18. The spring 16 is configured to apply elastic force to each of the upper and lower probes 12, 14.
FIG. 2 is a cross-sectional view illustrating a socket for inspection of a semiconductor package, in which a plurality of pogo pins is received in a dielectric body.
In FIG. 2, a socket 30 for inspection of a semiconductor package includes a plurality of pogo pins 10 and a dielectric body 20 which receives the plurality of pogo pins 10 separated a predetermined distance from each other.
The pogo pins 10 are received within the dielectric body 20 such that upper probes 12 protrude from an upper surface of the dielectric body 20 and lower probes 14 protrude from a lower surface of the dielectric body 20. The pogo pins 10 are arranged in the dielectric body 20 at the same intervals as those between external terminals 4 of a semiconductor package 2 which are brought into contact with the upper probes 12. The lower probes 14 are arranged at the same intervals as those of contact pads 8 of a test board 6 which is placed below the socket 30.
For inspection of the semiconductor package 2, the test board 6 is placed below the socket 30 and the semiconductor package 2 is placed above the socket 30. When the semiconductor package 2 is compressed, the external terminals 4 of the semiconductor package 2 are brought into contact with the upper probes 12 of the pogo pins 10, and the lower probes 14 are brought into contact with the contact pads 8 of the test board 6. The upper and lower probes 12, 16 are elastically supported towards upper and lower portions of the dielectric body 20 by the spring 16 in the pogo pin 10, respectively, so that the pogo pins 10 may electrically connect the semiconductor package 2 and the test board 6 to each other.
However, due to the reduced size, increased integration density and higher performance of the semiconductor package, the pogo pin for inspection of the semiconductor package has to be reduced in size accordingly and the socket for inspection of the semiconductor package using the pogo pin 10 also has to be reduced in size. In particular, the outer diameter of the pogo pin 10 has to be decreased according to a reduced distance between the external terminals of the semiconductor package 2.
Further, for the higher performance of the semiconductor package, the loss and distortion of an electric signal has to be minimized during transmission of the electric signal between the semiconductor package and the test board. In this case, the transmission path has to be in stable condition and the impedance of the transmission path has to be minimized.
However, a typical pogo pin is hardly likely to meet such requirements. For example, the transmission path may increase by the number of turns of the spring 14. Further, a great deal of undesired impedance may be created since the spring 14 exhibits relatively unsatisfactory electrical characteristics. Hence, the spring 14 is not suitable for the transmission path for the electric signal.
Accordingly, the pogo pin 10 transmits the electric signal through a transmission path passing through the upper probe 12, the cylindrical body 18 and the lower probe 14. However, the transmission path passing through the cylindrical body 18 may cause the following problem.
The upper and lower probes 12, 14 have to be smoothly vertically moved within the cylindrical body 18. In this case, the upper and lower probes 12, 14 received within the cylindrical body 18 have to have a smaller outer diameter than the cylindrical body 18. The cylindrical body 18 may be brought into too close contact with the upper and lower probes 12, 14, thereby causing increased contact resistance. In this case, the electric signal may be damaged or distorted in the transmission path. This may be serious when the electric signal has to be transmitted at high speed.